RT P1 45

See first we need to find the eqⁿ of the normal to the plane P₁ by finding the cross product of ( i + j ) and (i - 2j ) which comes out to be -3k
then similarly eqⁿ of the normal to the plane P₂ = 2i - 4j - 3k
then to find the eqⁿ of line passing through the intersection of the abv plane we need to find the cross product P₁ P₂..
which comes out to be12i + 6j..
now find dot product 12i + 6j with i -2j + 2k
cosθ = 0
so θ = π/2...
Ans B

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